Mean (± SEM) A parameter (closed circles) and b parameter (open circles) estimates following administration of ketamine (n = 17-23 per dose; a), MK-801 (n = 23 all doses; b), memantine (n = 20-23 per dose; c), CGS 19755 (n = 22 all doses; d), ifenprodil (n = 22-24 per dose; e), and D-cycloserine (n = 23 all doses; f). *p < .05, relative to vehicle. Note, if a subject’s data were excluded from one dose, data for the other doses were included in this figure because NLME analyses do not use listwise deletion when there are missing data.